The present invention broadly relates to the manufacture of containers, especially drawn and ironed containers made of steel or aluminum, such as those used in the food and beverage industry. More particularly, the present invention concerns the formation of a margin profile for an end closure that includes reinforcing rib structures the invention concerns both container lids and can bodies including integral domed end closures.
The need for packaging of food and beverage products for storage and sale has increased with the increase in human populations and as urbanization has intensified. In addition, the demand for convenient, ready-to-eat products have added to the demand for suitable packaging. A long standing technique for packaging certain foods and beverages is metal cans. Such cans take a variety of geometric shapes and are often produced out of drawn and ironed steel or aluminum. Typically, these containers are either circular, oval, or rectangular (including square) in cross-section and are used to package a wide variety of liquid beverages, fruit and vegetables, meat products, dehydrated foods, etc.
The rising demand for steel and aluminum containers, though, carries certain concerns about production costs and the quantity of material used in the fabrication process. Accordingly, there have been intensified efforts to reduce the wall diameter of steel and aluminum cans in order to reduce the weight and mass of raw material used to create a can of given volume. This saves in the costs of production in two ways. By reducing the quantity of material, lower raw material costs result. Moreover, the energy required to refine or recycle the material is reduced. Another advantage is a reduction in the need for virgin raw materials that must be extracted from the natural resource base. Indeed, due to the volume of cans, such as aluminum cans for example, even a very minor reduction in wall thickness can result in literally tens of millions of dollars in savings on an annualized base. This is additionally true if there can be a reduction in thickness of an aluminum lid that is typically seamed onto an aluminum can body since the seamed lid is substantially thicker than the can body.
Nonetheless, the reduction in wall thickness of containers is not without its problems. While a reduced wall thickness is highly desirable from a material standpoint, structural integrity of the container must be maintained. Since the reduced wall thickness of a container diminishes its inherent strength, improved geometries have been developed to give added strength of the design. An example of such a geometry in the beverage industry, is the formation of a concaved depression in the bottom of an aluminum can with this concaved depression being commonly referred to as a xe2x80x9cdomexe2x80x9d.
Providing the bottom of a container with an axial, internally extending dome has several advantages. The margin of the dome provides a U-shaped profile that increases the structural rigidity of the container, especially where the internal contents of the container are pressurized. The provision of a dome on such a container has allowed manufacturers to maintain adequate side wall and end wall strengths while reducing the thickness of the can blank material.
This is of particular importance to the beverage industry where carbonated beverages are packaged in the container for storage and sale. Here, the dome structure greatly increases the resistance of the container to expansion or xe2x80x9cbloatingxe2x80x9d so as to maintain integrity of the container while at the same time maintaining the contents of the container at the desired pressurized state. The lids that are seamed upon such can bodies also have a U-shaped margin that provides structural rigidity to the can.
In the typical production of a beverage can, a can blank is produced by stamping a cup-shaped blank out of sheet material. This cup-shaped blank has a bottom wall and side wall thickness that is greater than the thickness of the can to be produced, but the physical dimensions of the cup-shaped can blank are smaller than the can to be produced. The production blank is placed in an ironing device wherein a punch advances the can blank through drawing and ironing dies which configure the can blank into the final dimensions of the desired container. This is accomplished by stretching or xe2x80x9cironingxe2x80x9d the metal side walls of the can blank to increase its axial dimension while thinning the wall thickness to compensate for the increase in height. This device is commonly referred to as a xe2x80x9cbody makerxe2x80x9d. After the can body is created, a dome is configured in the integrally formed body end closure by a xe2x80x9cdomerxe2x80x9d. The domer can be associated with the body maker or can be a separate device. Where associated with the body maker, the bottom dome structure is formed at the end of the draw and iron cycle. Alternatively, the can body may be placed in a separate doming machine. In either case, a punch strikes the bottom end closure against a die structure that is configured to match the dome shape of the punch thereby to stamp the bottom profile in the container.
Even though significant advances have occurred in the formation of container structures, there needs to be continued advancement in this art in an effort to achieve the accommodates noted above. There is a continuing need for end closures, can bodies, containers and methods which allow the further reduction in material consumption without otherwise significantly compromising the integrity of the container system. The present invention is directed to these issues.
It is an object of the present invention to provide a new and useful end closure for a container where the amount of material used in construction is reduced yet where the structural integrity of the container is maintained.
It is another object of the present invention to provide a container with end closures, either in the form of a lid or an integrally formed bottom wall, that have improved strength.
It is yet another object of the present invention to provide a can body with a domed end closure of improved configuration for strength that may then be used to form a container.
Still a further object of the present invention is to provide a new and useful method of forming an end closure for a surrounding side wall of a container as well as a method for forming a canned body for such a container.
Yet a further object of the present invention is to provide for the possible reduction of materials used to form container, can bodies and end closures for such containers.
According to the present invention, then, an improvement is provided for a container that has a surrounding side wall forming a container body with a central axis and first and second end closures that define an interior. The improvement broadly includes at least one end closure for the container. The end closure has a central body panel oriented transversely to the central axis and an outer surrounding margin portion joined to the side wall. The margin portion includes a support section thereof that is oriented longitudinally relative to the container body. A plurality of rib structures are disposed on the margin and have longitudinally extending components located on the support section and positioned and spaced-apart relation therearound.
The rib structures are corrugated in nature and may be formed as flutes in the support section. Thus, the rib structures have trough regions separated by ridge portions. The trough regions, in one embodiment, are formed as tear-dropped shaped depressions in the support section. In another embodiment, the rib structures include a radial rib component disposed on the central body panel.
The margin portion of the enclosure may have a U-shaped profile to include an inner wall portion and an outer wall portion. The rib structures may be disposed either on the outer wall portion or on the inner wall portion. Where the end closure is an integrally formed bottom for the container body, formed as a one-piece construction with a side wall, the rib structures, for example, may be disposed on the inner wall portion. The rib structures may be equidistantly spaced from one another.
The support section on the margin portion of the central body panel may be a shell formed as a truncated geometric shape. This geometric shape may be cone or a pyramid having a polygonal base of xe2x80x9cnxe2x80x9d sides where xe2x80x9cnxe2x80x9d is an integer greater than two. As noted, the enclosure may be formed integrally with these side walls or, alternatively, may be a lid that is joined to the container body by a mechanical joint. The container body likewise may have a cross-section that is selected from a group consisting of circles, ovals and n-sided polygons where xe2x80x9cnxe2x80x9d is an integer greater than two. The central body panel can have a geometrical shape that is geometrically similar to the cross-section of the container body.
The present invention is also directed to a can body adapted to receive contents for packaging. The can body has a surrounding side wall portion having a central axis and a bottom closure joined to the side wall portion to enclose an end of the can body. The bottom closure includes a central body panel oriented transversely to the central axis and an outer surrounding margin portion joined to the side wall. This margin portion has a support section oriented longitudinally relative to the surrounding side wall body. A plurality of rib structures are then disposed in the margin and have longitudinally extending first rib components. These first rib components are located on the support section and are positioned in spaced-apart relation about the support section.
Here, again, the margin portion can have a U-shaped profile including an inner wall portion and an outer wall portion. The first rib component may be then disposed on the inner wall portion. Moreover, the inner wall portion may be formed as a truncated geometric shape, as described above. The first rib components can be flutes, such as tear-dropped shaped depressions in the support section. The other structures discussed above, can apply to this can body, as well. Where the can body is cylindrical, the rib components may be equiangularly spaced from one another. The invention also includes a container having a second end closure joined thereto that is opposite the first end closure.
The present invention also concerns a method of forming an end closure for a surrounding side wall of a container having a central axis. This method includes all of the steps inherent in the containers and can body noted above. The method can include a step of forming a central body panel oriented transversely to the central axis and an outer surrounding margin portion joined to the side wall with the margin portion having a support section oriented longitudinally relative to the side wall. The method can include the step of corrugating a portion of the margin to provide rib structures. At least some of the rib structures have longitudinally extending first rib components located on a support section. The method can also include the step of forming the support section as a truncated geometric shape, and this geometric shape may be a cone, or a pyramid having a polyigamol base of xe2x80x9cnxe2x80x9d sides where an xe2x80x9cnxe2x80x9d is an integer greater than two. The method can also include the configuring of the outer margin portion in a U-shaped profile to include an inner wall portion and an outer wall portion. The step of corrugating can be accomplished by forming the rib structures on the outer wall portion. Alternatively, the step of corrugating can be accomplished by forming the rib structures on the inner wall portion. The step of corrugating may be accomplished by forming flutes in the support section with these flutes, in one embodiment, being tear-dropped shaped depressions in the support section. The method can also include the formation of radial second rib components that are disposed on the central body panel.
The present invention is also directed to a method of forming a can body out of a cup-shaped can blank. Here, the method includes the step of ironing the can blank to form a surrounding side wall portion having a central axis and doming a bottom portion of the can blank. The doming of the bottom portion can be done to create a central body panel oriented transversely to the central axis and an outer surrounding margin portion joined to the side wall portion. The margin portion has a support section oriented longitudinally relative to the surrounding side wall body. The method can include the step of corrugating a portion of the margin to provide a rib structure having longitudinally extending first rib components located on the support section. This method can include the additional steps described, above, with respect to the formation of an enclosure.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiment of the present invention when taken together with the accompanying drawings, in which: